New guy here with a 1996, standard cab, short box, 2WD, 4.9, 5 speed, 143,000 miles. Just bought it and have just driven it 2,000 miles.

I think it may have an overheating issue as it heats up a bit at road speed when climbing interstate grades.....especially with A/C on.

Also, the A/C seems to shut off as the temperature gauge climbs. It turns back on as soon as the engine temp stabilizes or starts to decrease.

Should the stock cooling system be able to keep things cool running A/C, up a hill, on a hot day, at legal speed limits?

Does the A/C on this year truck normally have an automatic shut down feature?

Thanks for any thoughts.

 

I had the same problem. I installed a new fan clutch and the problem went away.

 

yes, the stock cooling system should be able to run AC at normal driving speeds on a hot day going up a hill. The only things that should strain the system are towing at max capacity on the hottest day of the year in Death Valley with the AC on max, and maybe extended idling on a very hot day with the AC on max.

It is normal for the AC clutch to engage and disengage periodically as the compressor is not required to be running constantly for AC operation.

when you say the AC shuts off as temp climbs, do you mean the air is no longer cool or that the clutch disengages and does not reengage?

 

Welcome to the site!

First suspicions are either a thermostat not opening fully, or a restricted radiator.

Once above, say, 25-30mph, the radiator fan really shouldn't be doing much other than freewheeling along for the ride.

Another possibility, although a bit of a reach, is that the water pump isn't up to snuff.

One way to check is to spin the fan, engine off of course. If you can spin it so that it freewheels more than 1/4-1/2 turn - clutch is probably not where it should be. Also, grab the tip of one of the fan blades and see if you can move it fore-and-aft. If so, verify the point of movement is at the clutch and not the water pump - then recommend replacing the clutch.

Have had pretty good luck with the less aggressive radiator flush products. These are the ones where you drain the coolant, put the stuff in, refill with water, and run around for a week or so. Then drain and thoroughly flush the entire system - heater core, block, and radiator - before refilling with the proper antifreeze mix. The more aggressive flushes tend not to be so healthy for aluminum radiators.

A 50/50 mix is the maximum one should run IMO, unless you're in the Great White North where I think a 70/30 blend is OK. The challenge is that the antifreeze is not as good at conducting heat as straight water.

Another thing to check is for good airflow through the A/C condenser and radiator. Bugs and debris can take their toll.

Wasn't aware of any A/C cutouts for high coolant temps on these models - but that is a feature presented on newer vehicles and could be present on your model year.

In short, the gauge may run a letter or two higher than usual on the N-O-R-M-A-L range during really hot weather, but shouldn't get to the point of overheating. Your description of heating up while going uphills is leading me back to a flow issue - whether it be coolant or air.

 

^^^ Good stuff. Also have your A/C Freon level checked. The compressor could be over taxed as a result of borderline low freon level, which makes it harder on the coolant system too. Also explaining the A/C low pressure switch eventually overriding the A/C system & shutting it down.

 

The A/C fan shuts off. I don't know if the entire A/C system shuts down but everything returns to normal as soon as the indicated temp starts to decrease as a hill is crested.

Thanks for the reply.

 

My fan definitely freewheels more than 1/4-1/2 a turn....but I thought that was normal. Isn't this type of viscous, centrifugal clutch supposed to freewheel until it gets warm....and then engage fully?

My original word...overheat...may have been a bit too excessive. I definitely saw the temperature gauge move to the upper range of the NORMAL scale. On level ground the gauge indicated slightly below midrange on the scale and the rise concerned me.....but it was a very hot day and I was traveling 65-70MPH with the A/C on. No trailer and no load in the truck....other than my 275#'s.

I don't know the history of my new truck but it has obviously had very good care. At 143K miles the fan clutch and water pump are probably due. I am too old to contort myself around a radiator anymore....plus I don't have the tools I need. Any ideas on what it may cost to have the work done professionally?

Thanks to all for your replies.

 

The A/C works well...at least it blows very cold air.

Doesn't that indicate the freon level is OK?

Thanks.

 

Regarding the freewheeling comment above, before I replaced the fan clutch, mine would freewheel a few revolutions before it came to a stop. When putting the new one on, it doesn't really freewheel at all.

What you are describing really sounds like a worn out fan clutch to me. I ended up going with a heavy duty fan clutch because it's cheaper than the standard duty. The HD clutch keeps it very cool, but sometimes it sounds like a heavy duty cargo van with that howl sound when I take off sometimes, so you might want to look at a standard duty fan clutch (if you choose to go that route) so that you won't have as loud of a howl.

 

My understanding is that the clutch is intended to lighten the load that the fan puts on the engine. Perhaps a slight difference between freewheeling as far as engine loading is concerned, and spinning freely.

A thought came to me that might be worth pursuing before shotgunning parts at the problem - your A/C system should be a R134 setup. Many of these came with a high pressure cutout in addition to the low pressure cut out. A high pressure cutout could mean that either there is too much freon in the system, or given your conditions, not enough heat being removed from the condenser.

One of the purposes of the low pressure cutout is to prevent the evaporator from freezing up. That's one of the challenges I still struggle with toward understanding A/C - a lower low side pressure relates to lower temperatures, but not as much total 'cold' flow since there is less freon present to move the heat.

A high pressure cutout might relate to the common cause between your engine high temps and the A/C cutting out - not enough airflow through the condenser / radiator to reject the heat???

As far as replacing the fan clutch - it's not too bad if you detach the fan shroud and just push it aft. Stranger things have happened, but not seeing the connection between a possible bad clutch and what you're experiencing moving on down the road. If the fan clutch were the problem, would expect the overheating issues to be experienced around town and stops???